Users are often required to login to authenticate their identity in order to access online accounts, computing devices, or other computing resources. Numerous authentication techniques exist. For example, before accessing a computing resource, a user may be required to provide a login name, email address, personal identification number (PIN), text-based password, picture password, digital certificate, physical access credential (e.g., smart card), phone number, biometric information (e.g., finger print, retinal scan, etc.), answers to one or more security questions, and/or other identifying information. Authentication has become a common requirement for almost everything users do on computers. However, these existing authentication techniques are burdensome, time consuming, error prone, and distracting to users. Many existing authentication techniques require the use of hands or voice, which makes them unusable by users with disabilities that impair the use of those faculties. Still further, many existing authentication techniques require multiple factors of authentication in order to increase security and to avoid attacks by computers or bots.